IRX2 is differentially expressed in the lymph nodes of patients with metastatic breast cancer.

Abstract

Metastasis to the brain is a clinical problem in patients with breast cancer (1-3). The lymph nodes reside between the breast and the brain. We mined published microarray data (4, 5) to compare primary and metastatic tumor transcriptomes for the discovery of genes associated with metastasis to the lymph nodes in humans with metastatic breast cancer. We found that the Iroqouis homeobox transcription factor IRX2 was among the genes whose expression was most quantitatively different in the lymph node metastases of patients with metastatic breast cancer as compared to primary tumors of the breast. IRX2 mRNA was present at increased quantities in lymph node metastases as compared to primary tumors of the breast. Importantly, expression of IRX2 in primary tumors of the breast was significantly correlated with patient recurrence-free survival. IRX2 differential expression was conserved when comparing normal breast and normal brain, suggesting that IRX2 modulation in lymph node metastatic tissues may perhaps reflect gene expression changes that facilitate metastasis to the brain in humans.